It is well documented that a variety of microorganisms are capable of utilizing L-carnitine as a sole carbon source. For example, it was reported that a bacterium (tentatively identified as a Pseudomonad), isolated from a polluted stream bed, utilized L-caritine from a DL-mixture to produce D-carnitine in high optical yield [G. Fraenkel and S. Friedman, Vitam. Horm. (N.Y.) 1957 16, 73]. Subsequently, the metabolism of D- and L-carnitine by resting cells of Pseudomonas putida and Acinetobacter calcoaceticus was investigated. Cells of Ps. putida grown on DL-carnitine degraded only L-carnitine with stoichiometric accumulation of glycine betaine [J. Miura-Fraboni and S. Englard, FEMS Microbiology Lett. 18 (1983) 113]. Some apparent controversy exists relative to the metabolism of carnitine by A. calcoaceticus. One report stated that this organism grew only on L-carnitine with the formation of trimethylamine [H. P. Kleber et al., Arch. Microbiol. 112 (1977) 201]. D-carnitine was metabolized, if an additional carbon source, like L-carnitine, was present in the incubation mixture, or if the bacteria were preincubated with L- or DL-carnitine, but no growth was observed on D-carnitine as the sole carbon source. On the other hand, J. Miura-Fraboni and S. England claimed that A. calcoaceticus utilized for growth both the D- and L-isomers of carnitine as sole carbon source with stoichiometric formation of trimethylamine, but, until the present invention no microorganisms have been reported which, in an incubation mixture containing DL-carnitine, preferentially degrade the unnatural form of carnitine, D-carnitine, resulting in the accumulation of the desired natural L-carnitine in the medium.
Also of interest is U.S. Letters Pat. No. 4,209,507 Ogino et al. which reports a variant strain of Acinetobacter Calcoaceticus var. microformis SC-1714 (ATCC-31299) from the culture of which in a suitable medium is derived a substance showing certain antitumor activity. Applicant has found that the Ogino et al. variant is ineffective to produce L-carnitine in accordance with the process of the present invention.